Tuesday, February 4, 2014

Alien Planets May Not Need Big Moons to Support Life

Alien planets without big, climate-stabilizing moons like the one that
orbits Earth may still be capable of supporting life, a new study
reports.

Previous modeling work had suggested that Earth's axial tilt,
or obliquity, would vary wildly over long time spans without the moon's
steadying gravitational influence, creating huge climate swings that
would make it tough for life to get a foothold on our planet.

"If the Earth did not have a moon, its obliquity — and, therefore, its
climate — would vary, indeed, substantially more than it does at
present," Lissauer said during a presentation in December at the
American Geophysical Union's annual fall meeting in San Francisco. "But
it's nowhere near as bad as was predicted based on previous models."

An abnormally large moon

Most researchers think the moon formed from material blasted into space when a mysterious planet-size body slammed into Earth nearly 4.5 billion years ago.

The moon
is 27 percent as wide as Earth and 1 percent as massive, making it a
celestial oddball. No other non-dwarf planet in the solar system harbors
a moon so large relative to itself, and such enormous satellites appear
to be rare farther afield as well, Lissauer said.

"If giant moons were common around exoplanets, then Kepler would've
found one by now," he said, referring to NASA's planet-hunting Kepler space telescope.